1. Field of the Invention
The present invention generally relates to the art of fluid flow control, and more specifically to an apparatus for detecting an opening in a fluid flow passageway and shutting off the flow in response thereto.
2. Description of the Related Art
In many fluid flow systems there is a high probability of a catastrophic opening or break at some point in the flow path which would allow the fluid to escape. For systems where this poses any type of risk it is desirable to have some method of break detection which allows for appropriate measures to be taken in a timely manner to stop or contain the escape of fluid.
An exemplary apparatus to which the present invention is especially applicable is a water cooling system for an resistance welding machine. Spillage of a substantial amount of water, especially in an environment of high electrical current, is not at all desirable.
An example of a leakage detection system is a human who is operating of a piece of liquid cooled equipment and sees the occurrence of a break in the cooling line and responds by shutting down the equipment and closing one or more valves to stop the coolant flow. In systems where there is no human presence, or human response is not quick enough or escaping fluid poses a human risk, some method of automatic detection is required which can then trigger an automatic response.
Breaks or openings in a fluid flow system are often detected by measuring a change beyond a predetermined level in either the fluid flow rate or pressure. The measurement can be made at either the inlet or outlet to the flow circuit. A break in the flow circuit will typically result in a pressure drop at both the inlet and outlet, a flow increase at the inlet, a flow decrease at the outlet and in cases where there is back pressure at the outlet, there may be a reverse in flow direction at the outlet.
Although sensing for one of these changes at a flow circuit's inlet or outlet is effective in many cases, there are instances where the detection system may be unreliable because of normally occurring variations in pressure at the flow circuit's inlet or outlet, or other factors such as multiple paths in the flow circuit or high pressure drops due to long or restricted paths. An unreliable system may result in either a failure to detect when a break occurs or a false indication of a break when none has occurred.